5.1

Question 1

Why can’t ions pass directly through the lipid bilayer?

Answer 1

Ions are hydrated (attract water), and the hydrophobic core of the membrane repels them.

Question 2

What does ion movement across membranes generate?

Answer 2

An electric current.

Question 3

What is the formula for current?

Answer 3

Current = ΔCharge / ΔTime.

Question 4

What is depolarisation?

Answer 4

A shift in membrane potential toward more positive values.

Question 5

What is hyperpolarisation?

Answer 5

A shift in membrane potential toward more negative values.

Question 6

Which ion is particularly important in signalling pathways?

Answer 6

Calcium (Ca²⁺).

Question 7

Where does signalling calcium come from?

Answer 7

Extracellular space or intracellular stores.

Question 8

What types of pathways does calcium influence?

Answer 8

Immune response, muscle contraction, neurotransmitter release, etc.

Question 9

What are ion channels?

Answer 9

Proteins that form water-filled pores to allow passive ion movement.

Question 10

What do ion channels do?

Answer 10

Conduct ions, select specific ions, and open/close in response to signals.

Question 11

How fast can ion channels conduct ions?

Answer 11

Up to 100 million ions per second.

Question 12

What determines ion selectivity in channels?

Answer 12

Pore size and chemical interactions within the pore.

Question 13

What is gating in ion channels?

Answer 13

The process of opening and closing ion channels.

Question 14

What are the four main types of ion channel gating?

Answer 14

Ligand-gated, voltage-gated, phosphorylation-gated, and stretch-activated (mechanotransduction).

Question 15

What determines ion flow through a channel?

Answer 15

The electrochemical concentration gradient.

Question 16

What is conductance?

Answer 16

A measure of how much charge (or how many ions) moves through a channel.

Question 17

What happens to conductance as equilibrium is approached?

Answer 17

It decreases.

Question 18

What are some pharmacological targets on ion channels?

Answer 18

Ligand binding, gating mechanisms, intracellular regulators (e.g., ATP), and second messenger systems.

Toxins affect gating,
2nd msg affect phosphorylation of channel
ATP-o/c

Question 19

What do toxins do to ion channels?

Answer 19

Block them or alter their gating.

Question 20

What do membrane transporters do?

Answer 20

Move ions or small molecules across membranes, usually slower than ion channels.

Question 21

How fast do transporters work?

Answer 21

Up to 3 molecules per second.

Question 22

When is ATP needed for transport?

Answer 22

When substances move against their concentration gradient (active transport).

Question 23

What are the three types of active transporters?

Answer 23

P-type, V0V1-type, ABC-type.

Question 24

What do P-type transporters include?

Answer 24

Ion pumps like the sodium/potassium pump.

Question 25

How do active transporters use energy?

Answer 25

Convert ATP to ADP to move substances against their gradients.

Question 26

How does secondary active transport differ from primary?

Answer 26

It does not use ATP directly.

Question 27

What powers secondary active transport?

Answer 27

Energy stored in the concentration gradient of another ion.

Question 28

What are SLC transporters?

Answer 28

Solute carrier transporters, often functioning as symporters or antiporters.

Question 29

What’s the difference between symport and antiport?

Answer 29

Symport: substances move in same direction; Antiport: substances move in opposite directions.

Question 30

What makes neurons electrically excitable?

Answer 30

The selective movement of ions across membranes.

Question 31

What are the intracellular ion concentrations in neurons?

Answer 31

High K⁺, low Na⁺, and low Cl⁻.

Question 32

What is an action potential?

Answer 32

A rapid electrical impulse generated by ion movement across the neuronal membrane.

Question 33

What causes neurotransmitter release?

Answer 33

The arrival of an action potential at the axon terminal.

Question 34

What is a synapse?

Answer 34

The junction where a neuron communicates with another cell via neurotransmitter release.

Question 35

How do neurotransmitters act?

Answer 35

By binding to ion channels and receptors on the post-synaptic membrane.

Question 36

How are neurotransmitters removed from the synapse?

Answer 36

By reuptake through transporters or enzymatic degradation.

Question 37

What are the four steps of neurotransmission?

Answer 37

1. Synthesis and storage of NT in presynaptic neuron (vesicles) 2. Release of NT by presynaptic neuron to synaptic cleft (through stimulus) 3. Interaction of NT with receptors (channels/trans) for signalling 4. Removal of NT | Synthesis/storage, Release, Receptor/ion channel interaction, Removal.

Question 38

Can neurotransmitters act on presynaptic cells too?

Answer 38

Yes, they can modulate their own release via autoreceptors.